Conventionally, in the analysis of motion of a continuum to examine the flow of fluid, such as water or air, by using numerical calculations, i.e., in the fluid analysis, a technology called a particle method has been proposed. Specifically, the particle method is a technique in which the motion of a continuum is analyzed as the motion of a finite number of particles. Typical particle methods that have recently been proposed include the Smoothed Particle Hydrodynamics (SPH) method and the Moving Particle Semi-implicit (MPS) method. In the following, fluid, such as water or air, may be referred to as a “continuum”.
As a standard technique used in the particle method, there is a known technique in which a region (hereinafter, described as an “influence region”) is set in advance with respect to a particle of interest and a force applied to the particle of interest is obtained by calculating interactions between the particle of interest and other particles that are present in the influence region.
In particular, the feature of the SPH method used to express a continuum is that the physical quantities of a plurality of particles are approximated by a smoothing process using a weight function called a kernel function in order that a primitive equation is discretized. With the smoothing process, it becomes possible to eliminate a calculation process of cumbersome mesh operations including evaluation of the physical quantities on mesh points. Therefore, the SPH method is suitable for dealing with a free surface problem to analyze free surface flows or a multi-physics problem to analyze a plurality of physical phenomena represented by different governing equations.
Therefore, for example, the SPH method is considered to be suitable for estimation of the flow velocity and the impact pressure of sea waves that hit or overreach revetments.    Non-Patent Document 1: J. J Monaghan, “Smoothed Particle Hydrodynamics”, Annu. Rec. Astron. Astrophys., Vol. 30, pp. 543-574    Non-Patent Document 2: Yukihito Suzuki, Seiichi Koshizuka, Yoshiaki Oka, “Development of Hamiltonian Moving Particle Semi-implicit (HMPS) Method (Implementation of a Symplectic Scheme”, Trans. JSCES, Paper No. 20050017 (2005)    Non-Patent Document 3: Paul W. Cleary, “Modelling confined multi-material heat and mass flows using SPH”, Appl. Math. Modelling, Vol. 22, pp. 981-993, 1998    Non-Patent Document 4: M. G. Gesteira, B. D. Rogers, R. A. Dalrymplem, A. J. C. Crespo, M. Narayanaswamy, “User Guide for the SPHysics Code, September 2010”, pp. 9-15    Non-Patent Document 5: Fang, J., Parriaux, A., Rentschler, M., Ancey, C., “Improved SPH methods for simulating free surface flows of viscous fluids”, Applied Numerical Mathematics, Vol. 59, pp. 251-271, 2009    Non-Patent Document 6: Morris, J., Fox, P. J., Zhu, Y., “Modeling Low Reynolds number incompressible flows using SPH”, J. comp. Phys., Vol. 136, pp. 214-226, 1997
However, in the simulation using the conventional particle method, if surface wave propagation is dealt with for a long time, surface wave attenuation occurs. Regarding this matter, wave propagation was actually analyzed by using the standard SPH method, and it was found that large wave-height attenuation has occurred after a lapse of a predetermined time and wave generation tests was not be simulated. As described above, in the simulation using the conventional particle method, deviation from the reality becomes large. Therefore, it is difficult to reduce the number of hydraulics model tests of generating waves by a wave generation board that is set in an actual water tank.